If you’re comparing plastic materials, you’ll quickly come across two main categories: thermoplastics and thermosets.
The fundamental difference is that thermoplastics can be remelted, reshaped and reused multiple times, whereas thermosets, once cured, are permanently set and can’t be remoulded.
This page explains the differences in the composition of these materials and how it impacts everything from cost to performance and applications.
What are thermoplastics?
Thermoplastics are polymer materials made up of long, linear or lightly branched molecular chains. These chains aren’t chemically bonded to each other. Instead, they’re held together by relatively weak intermolecular forces.
When you apply heat, those weak forces loosen, allowing the chains to slide past one another. This is what causes the material to soften and become mouldable. When the material cools, the forces reestablish, and the chains lock back into place, returning the material to a solid state.
Crucially, because there are no permanent chemical crosslinks between the chains, this process can be repeated many times without significantly changing the material’s structure. In other words, thermoplastics can be melted and reshaped, again and again.
This is what makes them so useful in manufacturing. Because the material can be reheated without noticeable degrading, it can be processed quickly, reused if needed, and produced in large volumes with consistent results. That’s why thermoplastics are typically chosen for applications where production efficiency, adaptability and cost control are important.
Some examples of thermoplastics include Polypropylene (PP), polyethylene (PE – HDPE/LDPE), acrylonitrile butadiene styrene (ABS), polycarbonate (PC), polyamide (nylon – PA6/PA66), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polystyrene (PS), polyoxymethylene (POM/acetal) and polymethyl methacrylate (PMMA).
Typical applications:
- Food and beverage packaging (containers, bottles, films)
- Medical devices (syringes, tubing, protective equipment)
- Consumer goods (toys, household items, storage products)
- Electrical insulation and cable coatings
- Textiles and clothing (synthetic fibres and waterproof fabrics)
- Agricultural systems (irrigation pipes, greenhouse coverings)
You’ll also find thermoplastics widely used in engineering, due to their corrosion resistance, low weight and design flexibility.
What are thermoset materials?
Thermosets behave very differently. Instead of softening repeatedly, they undergo a chemical curing process that permanently sets their shape.
At a molecular level, thermosets start as small molecules or short polymer chains. During curing, they react, forming covalent bonds and a tightly crosslinked network, transforming these chains into a rigid, three-dimensional structure.
With these bonds in place and the structure ‘locked in’, the chains can no longer flow past each other. Instead of softening, the material will retain its shape until, at sufficiently high temperatures, it begins to degrade rather than melt.
This is why thermosets can’t be remoulded or recycled in the same way as thermoplastics. The curing process is irreversible, and the structure is permanently fixed.
However, that same structure is why thermosets provide excellent heat resistance, chemical stability, and dimensional strength under load. That’s why manufacturers typically select thermosets for high-stress applications and conditions.
Some examples of thermosets include epoxy resins, phenolic resins, polyester resins (unsaturated polyester), polyurethane (thermoset PU), melamine formaldehyde, urea formaldehyde, vinyl ester resins and silicone resins.
Typical applications:
- Electrical components (circuit boards, insulators, switchgear)
- Construction materials (adhesives, coatings, insulation, composite panels)
- Aerospace and high-performance composites (structural parts, interiors)
- Industrial equipment (valves, seals, pumps, heat-resistant components)
- Household and kitchen products (laminates, durable kitchenware)
- Energy and infrastructure systems (oil, gas, and power distribution components)
Thermoplastic vs thermoset: the key differences
If you’re deciding between thermoplastic and thermoset materials, the differences go beyond the names. Your choice will affect how a part performs in service, how it’s processed, and what you can (realistically) use it for. So, it’s worth understanding where the two diverge:
- Heat behaviour: Thermoplastics soften and can be reshaped. Thermosets permanently cure and can’t be reprocessed.
- Reusability: Thermoplastics can be recycled and reused. Thermosets can’t be remelted.
- Processing: Thermoplastics are typically used in injection moulding, as they suit fast, repeatable cycles and high-volume production. Thermosets are typically used in compression moulding, as it applies heat and pressure evenly during curing.
- Performance: Thermoplastics tend to be more flexible with greater toughness. Thermosets offer higher heat resistance and structural rigidity.
- Typical use case: Thermoplastics are ideal for high-volume, cost-efficient parts. Thermosets are used in high-performance or high-temperature environments.
When should you use thermoplastics vs thermosets?
Use thermoplastics when you need high-volume manufacturing, lower unit costs at scale, and the ability to refine designs over time. They’re well suited to applications requiring impact resistance, flexibility and recyclability, and are particularly effective in injection moulding.
Use thermosets when your priority is performance under stress. They’re better suited to components exposed to high temperatures, chemical environments or electrical loads, where structural rigidity and long-term durability are more important than reusability or production speed. In most cases, thermosets are used in compression moulding, along with other curing-based processes.
Which material is right for your application?
To answer that, ask one simple question: what does your part need to do?
You need to consider the operating environment, including exposure to heat, chemicals, or electrical loads, as well as the mechanical demands of the component. Don’t forget to factor in the production volume, alongside the balance between cost and performance.
In many cases, especially for large production runs, thermoplastics are the preferred choice. However, for specialised, high-performance applications, thermosets are irreplaceable.
Need help choosing the right material?
If you’re developing a plastic component or doing some early research, it’s worth getting expert input early on. And that’s where we come in.
At Talisman Group, we provide end-to-end support, from material selection and design for manufacture through to tooling and full-scale production. With expertise in both injection moulding and compression moulding, we can help you choose the right process and material for your application, not just the most convenient option.
With the right material and manufacturing process in place, you can tailor your designs, streamline production, improve reliability and avoid costly redesigns. So, if you’re unsure which direction to take, schedule a commitment-free discovery call with our team today.